Someone

Function GetValidPlayerName(OtherPlayer:String) : String;
  Var
    PlayerName : String;
  Begin
    Repeat
      Readln(PlayerName);
      If PlayerName = '' OR PlayerName = OtherPlayer
        Then Write('That was not a valid name.  Please try again: ');
    Until PlayerName <> '' AND PlayerName <> OtherPlayer;
    GetValidPlayerName := PlayerName;
  End;